Evaluation of a Dynamic Variable Orifice for Reciprocating Compressor Pulsation Control
Fixed orifice plates are effective in reducing reciprocating compressor pulsations over a narrow compressor operating range, however there is an associated pressure drop that adds to power consumption required by the compressor. Many applications require operation over a wide range of speed, pressure and flow conditions that may vary from low to very high flows. The system pulsation control design for such applications is almost always a compromise between pulsation control and pressure drop or power penalties. Although one or more fixed orifice plates having specific diameters may be necessary and effective for pulsation control at one set or a range of operating conditions, they may be ineffective and/or cause unacceptably high pressure drop and associated power consumption at other ranges of operating conditions. Therefore, it would often be advantageous to change one or more fixed orifice plate diameter(s) as operating conditions change. Yet, it is rarely considered as an alternative to extending range or improving efficiency, because it requires system depressurization, gas venting, manual labor and significant downtime. This paper introduces a new technology, a dynamic variable orifice (DVO), for controlling pulsations and pulsation induced unbalanced forces in reciprocating compressor systems. The DVO can be manually of automatically adjusted while the compressor is pressurized and operating. This allows the orifice size to be set for optimal pulsation control and efficiency as conditions change. Basic mechanical features, installation requirements, and operation of the DVO are described. Results of an extensive acoustic analysis case study of large reciprocating compressors in central gas gathering compression applications are presented. The study quantifies the trade-offs and limitations in pulsation control, pressure drop and power consumption associated with a fixed set of orifices used over typical ranges of required operating conditions. It also quantif
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